The application is a continuation of applications titled “Multi-Spectrum Photosensitive Devices and Methods for Manufacturing the Same” (PCT/CN2007/071262), and “Multi-Spectrum Photosensitive Devices and Methods for Manufacturing the Same” (Chinese Application No. 200810217270.2) filed by the present inventor(s), and aims at providing more specific and preferable semiconductor circuit-level and chip-level implementations.
The previous photosensitive devices relate to sensing color visible lights or infrared, while seldom sensing both of them simultaneously. Although some other inventions or applications, such as a cadmium indium based semiconductor technology (“Silicon infrared focal plane arrays”, M. Kimata, in Handbook of Infrared Detection Technologies, edited by M, Henini and M. Razeghi, pp. 352-392, Elsevier Science Ltd., 2002), may also be used to implement simultaneous photosensing for both invisible lights and infrared, but no color has been achieved. The previous methods for obtaining photosensitivity of color lights and infrared at the same time is to physically superimpose a color photosensitive device and a infrared photosensitive device together (such as, “Backside-hybrid Photodetector for trans-chip detection of NIR light”, by T. Tokuda et al., in IEEE Workshop on Charge-coupled Devices & Advanced Image Sensors, Elmau, Germany, May 2003, and “A CMOS image sensor with eye-safe detection function backside carrier injection”, T. Tokuda et al., J. Inst Image Information & Television Eng., 60(3): 366-372, March 2006).
A new method for manufacturing multi-spectrum photosensitive device in order to obtain color and infrared images simultaneously is proposed in the previous application titled “Multi-Spectrum Photosensitive Devices and Methods for Manufacturing the Same” (PCT/CN2007/071262), and “Multi-Spectrum Photosensitive Devices and Methods for Manufacturing the Same” (China Application No. 200810217270.2) filed by the present inventor. In the new-type photosensitive devices, dynamic photosensitive ranges of photosensitive devices are greatly expanded so as to meet high performance requirements in the fields of vehicles, security and surveillance etc. Furthermore, they can be used in small-sized color photosensitive devices, such as cell phone cameras, and the quality of image may be greatly enhanced. In addition, they can be manufactured by applying manufacturing technologies of existing CMOS, CCD, or other semiconductor photosensitive devices, and many effective manufacturing methods and structure designs can be used in these technologies. Some manufacturing methods using CMOS/CCD semiconductor technologies are provided in the present application.
However, a new problem brought from this new double-layer or multi-layer photosensitive device is that the data volume is two times or even more than that of conventional single-layer photosensitive devices. Although only half pixels may be needed to obtain the same resolution of double-layer photosensitive devices as that of single-layer photosensitive devices, processing large-array data in photosensitive devices at high speed remains a problem to be improved.
Recently, some excellent methods for sub-sampling large-array images with high performance, such as shared readout circuit, row binning and column binning sampling technologies are proposed in some applications, for example U.S. Pat. Nos. 6,801,258B1, 6,693,670B1, 7,091,466B2, 7,319,218B2 and etc. Among these applications, U.S. Pat. Nos. 6,693,670B1, 7,091,466B2, and 7,319,218B2 are worth mentioning, which provide some effective and simple approaches to implement the binning of N columns or N rows, or that of M columns and N rows.
However, these technologies are still not optimal. For example, the signal-to-noise ratio (SNR) of image is only improved to √{square root over (N)} times by combining N points into one through using the row binning and column binning sub-sampling operations (see U.S. Pat. Nos. 7,091,466B2 and 7,319,218B2). This is because the signals are just averaged in the row and/or column binning operations, thereby decreasing the variance of random noise only by √{square root over (N)} times, while the useful signals themselves are not strengthened and are just substituted by the average value of several points. Moreover, there usually exist slowly-varying and low-frequency noise in image signals, which are not decreased neither.
In addition, the existing sub-sampling technologies only concern the requirements of sub-sampling of photosensitive chip arranged in Bayer pattern or CYMG pattern separately, and make no simplification in the post-sampling processing. For example, a color image of Bayer pattern remains to be an image of Bayer pattern by using the row binning and column binning sampling operations (see U.S. Pat. Nos. 7,091,466B2 and 7,319,218B2) employed by U.S. Micron Technologies Inc., and then to obtain YUV images which are preferred in preview and storage stages, complex processes are still required. While some other sub-sampling circuits can improve SNR, they need complex integrating circuits and comparators, thereby increasing auxiliary circuit and frequency.
Another significant limitation in existing sub-sampling technologies is that the row binning and column binning operations are only applied in pixels sensing the same color, wherein the pixels are not immediately contiguous in space (i.e., other pixels may be interposed therebetween). For Bayer patterns or CYMG color patterns, pixels of same color are not immediately contiguous in space, and the characteristic of uniform spatial distribution of original images has been damaged by the row binning and column binning operations. Therefore, the aliasing effects are easily generated in edges of lines if the backend processing is not specifically adapted to this situation.
In particular, for double-layer or multi-layer photosensitive devices to be concerned in the present application, the prior arts look quite awkward and mediocre because the double-layer or multi-layer photosensitive devices provide a lot excellent but totally new color pattern arrangements, for which both signal read out and sub-sampling should make use of the characteristics of the double-layer or multi-layer photosensitive devices so as to make improvements.